You can buy grooved mdf, designed for bending. It's quite rigid in one direction only.
Grooves inside are good for breaking up reflections, and is done on higher end cabinets sometimes.
Some perforated sheet, such as supplied for radiator boxes at home might be of use. Trying to gain volume this way is really pushing the boundary's though.
Grooves inside are good for breaking up reflections, and is done on higher end cabinets sometimes.
Some perforated sheet, such as supplied for radiator boxes at home might be of use. Trying to gain volume this way is really pushing the boundary's though.
Hi Niels,
I wouldn't do that. Lightly stuff the box completely with pink fiberglass. That will make the speaker think it has up to 10% more volume. A sealed box (not ported) would be the enclosure type.
Often people put too large a driver in a box. The speaker should have a smaller woofer than you would commonly see in a store. You want the system "Q" to be somewhere between 0.7071 and 1.00. Otherwise you really risk having a boomy box that doesn't have deep bass.
-Chris
I wouldn't do that. Lightly stuff the box completely with pink fiberglass. That will make the speaker think it has up to 10% more volume. A sealed box (not ported) would be the enclosure type.
Often people put too large a driver in a box. The speaker should have a smaller woofer than you would commonly see in a store. You want the system "Q" to be somewhere between 0.7071 and 1.00. Otherwise you really risk having a boomy box that doesn't have deep bass.
-Chris
All that anatech says. Pick the size and expectations to fit each other. You can't stuff large bass in a small box any more than 10 pounds potatoes in a 5 pound bag.
The increase of volume from hogging-out will be small.
The decrease of stiffness and mass may be significant.
Unless you need router-shavings, I'd say don't.
Using round fat numbers: 7" box of 0.7" wood. 5.6" inside. Shave out half of each panel (grooves 95% deep over 53% of surface). You gain 0.7" total. 6.3" equivalent inside. It is only about 5% difference in F and Q, hardly significant. Even if done all 5/6 sides.
And a box those proportion is silly. Use 0.375" panels, even 1/4" with a few slats.
The increase of volume from hogging-out will be small.
The decrease of stiffness and mass may be significant.
Unless you need router-shavings, I'd say don't.
Using round fat numbers: 7" box of 0.7" wood. 5.6" inside. Shave out half of each panel (grooves 95% deep over 53% of surface). You gain 0.7" total. 6.3" equivalent inside. It is only about 5% difference in F and Q, hardly significant. Even if done all 5/6 sides.
And a box those proportion is silly. Use 0.375" panels, even 1/4" with a few slats.
Chris.
Stuffing the box with pink fiberglass sounds interesting, I will definitely try this.
In the design I have now, the box is ported. I'm new to speaker building, but I was of the understanding that I would be able to push some deeper bass with the port.
The purpose of the speaker is to build a bluetooth speaker, in my own design, with the equivalent or better sound than the "high-end" (~$600) bluetooth speakers that you can buy in the stores. I have a Bang & Olufsen Beolit 12 as reference.
I initially used a Monacor SPH-100C. It sounded absolutely fantastic, after I flattened the frequency response with a miniDSP, but it simply couldn't play loud enough. I have now ordered a SPH-135KEP which should have significantly less bass in the same cabinet size, but should be able to play quite a bit louder.
As you can probably read out of my post, I'm looking to build a speaker that doesn't necessarily play 100% correct, but rather a speaker that has a wow factor to the average (non-hifi enthusiast) listener.
Do you have any suggestions to how to accomplish this goal?
-Niels
Stuffing the box with pink fiberglass sounds interesting, I will definitely try this.
In the design I have now, the box is ported. I'm new to speaker building, but I was of the understanding that I would be able to push some deeper bass with the port.
The purpose of the speaker is to build a bluetooth speaker, in my own design, with the equivalent or better sound than the "high-end" (~$600) bluetooth speakers that you can buy in the stores. I have a Bang & Olufsen Beolit 12 as reference.
I initially used a Monacor SPH-100C. It sounded absolutely fantastic, after I flattened the frequency response with a miniDSP, but it simply couldn't play loud enough. I have now ordered a SPH-135KEP which should have significantly less bass in the same cabinet size, but should be able to play quite a bit louder.
As you can probably read out of my post, I'm looking to build a speaker that doesn't necessarily play 100% correct, but rather a speaker that has a wow factor to the average (non-hifi enthusiast) listener.
Do you have any suggestions to how to accomplish this goal?
-Niels
Sure! That would be no problem at all. I'm still just toying around.
I guess I owe you some volume details. At the moment the volume is 6.2L, but I'm considering pushing it to 7.7L by changing the dimensions slightly.
-Niels
> volume is 6.2L.... pushing it to 7.7L
SPH-135KEP
Resonant frequency (fs) 45 Hz
Total Q factor (Qts) 0.30
Equivalent volume (Vas) 15.5 l
Linear excursion (XMAX) ± 3.25 mm
Type of speaker 5.25"
The difference 6.2l or 7.7l is just over a semi-tone.
15.5l speaker in a 7l sealed box, both Fs and Q will come up factor of 3.14.
So Q becomes 0.94, Fs becomes 141Hz. This is a slight rise becoming 3dB down at 113Hz.
This is near the "maximum efficiency" of a seal-box, most bass for the least box. The peak would be nearer Q=1.1, but that puts F3 up at 150Hz, over an octave of pop-bass missed.
Basically it is a 5-1/2" speaker in a 7" box and will NOT pump huge bass. It may be quite gorgeous from mid-bass on up. (You should know I am a fan of large speakers; 18" for starters. Yes, they don't fit in the car.)
The 3mm excursion is large, but if midrange is covered by the same cone the IM distortion will be significant even at 1mm excursion.
Rule of thumb: a sealed box often works (for obscure reasons) when cube-root of box volume is 1.1-1.2 times speaker advertised diameter. Vented-box needs more space than this, a larger box. You have a 7.5"^3 box and a 5.5" speaker, a 1.36:1 ratio. There may be a slight advantage in venting. Problem is that the cone un-loads below box resonance in a range where pop-music has great power. It wants to flap. (DSP may cut this.) I'd look to the "step-down" tunings where box is tuned low, response allowed to droop, but driver stays loaded another part-octave lower.
Model it up in thin cheap chipboard. See how it plays. It may come out a little better when done right, but no big WOW change.
SPH-135KEP
Resonant frequency (fs) 45 Hz
Total Q factor (Qts) 0.30
Equivalent volume (Vas) 15.5 l
Linear excursion (XMAX) ± 3.25 mm
Type of speaker 5.25"
The difference 6.2l or 7.7l is just over a semi-tone.
15.5l speaker in a 7l sealed box, both Fs and Q will come up factor of 3.14.
So Q becomes 0.94, Fs becomes 141Hz. This is a slight rise becoming 3dB down at 113Hz.
This is near the "maximum efficiency" of a seal-box, most bass for the least box. The peak would be nearer Q=1.1, but that puts F3 up at 150Hz, over an octave of pop-bass missed.
Basically it is a 5-1/2" speaker in a 7" box and will NOT pump huge bass. It may be quite gorgeous from mid-bass on up. (You should know I am a fan of large speakers; 18" for starters. Yes, they don't fit in the car.)
The 3mm excursion is large, but if midrange is covered by the same cone the IM distortion will be significant even at 1mm excursion.
Rule of thumb: a sealed box often works (for obscure reasons) when cube-root of box volume is 1.1-1.2 times speaker advertised diameter. Vented-box needs more space than this, a larger box. You have a 7.5"^3 box and a 5.5" speaker, a 1.36:1 ratio. There may be a slight advantage in venting. Problem is that the cone un-loads below box resonance in a range where pop-music has great power. It wants to flap. (DSP may cut this.) I'd look to the "step-down" tunings where box is tuned low, response allowed to droop, but driver stays loaded another part-octave lower.
Model it up in thin cheap chipboard. See how it plays. It may come out a little better when done right, but no big WOW change.
Hi Niels,
Both Cal and PRR are bang on the money. With such a high cut-off frequency you really need to keep with a sealed box. Also keep in mind that any boost that DSP creates will severely limit the average loudness of the system. Use the DSP to tame peaks in the response and accept the low end limit. You can force the system to have lower frequencies, but that will result in higher distortion and also a lot more power required to get that performance.
Like PRR and Cal, I am a believer in large enclosures where the natural low cut-off frequency allows for a ported box design. Normally that means you want to have a low frequency cut-off in the low 30 Hz or lower. I'm talking about a -3dB level, not the -10dB or -20dB levels you see in most speaker system specifications. Once you live with a system like that, it is really difficult to go back to the more common speakers you see people with.
Speakers are just heavy boxes of air from a shipping standpoint. This is the main reason why most store bought speakers have boxes 1/2 the size they should be, that ratio is even smaller if you are looking at a ported system. The reality of this means that to get a system that works as it should you are going to have to build it yourself with speakers (drivers) that are marketed for the express purpose of having people building the system from scratch. People like Solen in Quebec, Canada, are excellent to deal with and they will design the box and crossover at no charge as long as you buy the parts from them. Pretty reasonable if you ask me. I have dealt with them over many years, but have never had them design any part of a system for me.
So, to sum up, for a small box that you want, it will probably be a sealed system - definitely not ported! Your DSP will be used to flatten peaks in the response, but not to amplify or extend bass response. If you can design this properly you shouldn't need a DSP to help out with the end response.
Amplifying bass will cost you dearly in increased power and higher distortion. Don't attempt this as it just gets worse the deeper you attempt to have the bass response to go down to. Use a good tweeter and woofer as those parts will do more to get you where you want to be than any DSP tricks ever will. Consider bi-amping the speaker as then you have an electronic crossover and the tweeter amplifier does not have to deal with any bass. This will greatly increase efficiency as you aren't losing power in the passive crossover type. It will also sound a great deal better. Try that and you won't go back to using a single amplifier and crossover.
-Chris
Both Cal and PRR are bang on the money. With such a high cut-off frequency you really need to keep with a sealed box. Also keep in mind that any boost that DSP creates will severely limit the average loudness of the system. Use the DSP to tame peaks in the response and accept the low end limit. You can force the system to have lower frequencies, but that will result in higher distortion and also a lot more power required to get that performance.
Like PRR and Cal, I am a believer in large enclosures where the natural low cut-off frequency allows for a ported box design. Normally that means you want to have a low frequency cut-off in the low 30 Hz or lower. I'm talking about a -3dB level, not the -10dB or -20dB levels you see in most speaker system specifications. Once you live with a system like that, it is really difficult to go back to the more common speakers you see people with.
Speakers are just heavy boxes of air from a shipping standpoint. This is the main reason why most store bought speakers have boxes 1/2 the size they should be, that ratio is even smaller if you are looking at a ported system. The reality of this means that to get a system that works as it should you are going to have to build it yourself with speakers (drivers) that are marketed for the express purpose of having people building the system from scratch. People like Solen in Quebec, Canada, are excellent to deal with and they will design the box and crossover at no charge as long as you buy the parts from them. Pretty reasonable if you ask me. I have dealt with them over many years, but have never had them design any part of a system for me.
So, to sum up, for a small box that you want, it will probably be a sealed system - definitely not ported! Your DSP will be used to flatten peaks in the response, but not to amplify or extend bass response. If you can design this properly you shouldn't need a DSP to help out with the end response.
Amplifying bass will cost you dearly in increased power and higher distortion. Don't attempt this as it just gets worse the deeper you attempt to have the bass response to go down to. Use a good tweeter and woofer as those parts will do more to get you where you want to be than any DSP tricks ever will. Consider bi-amping the speaker as then you have an electronic crossover and the tweeter amplifier does not have to deal with any bass. This will greatly increase efficiency as you aren't losing power in the passive crossover type. It will also sound a great deal better. Try that and you won't go back to using a single amplifier and crossover.
-Chris
That is some very valid points from both of you, and some good rules of thumb! Thank you very much!
I guess building an "under-sized" speaker will always bring some compromises. I did a bit more research yesterday, and figured out, that all of the "good" bluetooth speakers out there, makes use of a Passive Radiator design and not a completely closed design. - From what I can read, this should be able to boost the bass-line a tad compared to a closed design.
The SPH-100C would in theory be great with this particular speaker size, it just doesn't play loud enough.
If any of you have a suggestion for a good unit, with decent bass and loudness, that would fit this volume size, I would be grateful
.
-Niels
I guess building an "under-sized" speaker will always bring some compromises. I did a bit more research yesterday, and figured out, that all of the "good" bluetooth speakers out there, makes use of a Passive Radiator design and not a completely closed design. - From what I can read, this should be able to boost the bass-line a tad compared to a closed design.
My calculations based on the TS parameters shows that this particular unit should work with a ported design with a volume of 6.3L and a closed design of 3L. I have double-checked the parameters, but maybe I have foreseen something.
The SPH-100C would in theory be great with this particular speaker size, it just doesn't play loud enough.
If any of you have a suggestion for a good unit, with decent bass and loudness, that would fit this volume size, I would be grateful
.-Niels
I have done some more research, and it seems that a passive radiator is the best trade-off in a small volume box like mine.
I have read here on the forum, that the Morel MW144 5" Woofer is a great choice for small volume closed boxes. It has a standard design, in a closed box, of 8.2L with a F3 at 73hz and a "Q" at 0.7.
I have a made a simulation with a cheap Dayton Audio ND105-PR passive radiator, and it yields the F3 a 61hz, which is more or less what I'm looking for.
I have read somewhere that a "rule of thumb" is to use a passive radiator twice as big as the woofer (or two at the same size). This is unfortunately not possible in my design, and doesn't seem to change the F3 in the simulations either.
In most designs the PR is places on the side of the box, but would it be okay to place it just above the woofer as shown here:
I must admit that it is quite challenging and takes a lot of research to build a speaker in the sub 15L area, with both good loudness and a "deep" bass.
If any of you have some good recommendations for the woofer or PR it would be a great help
-Niels
I have read here on the forum, that the Morel MW144 5" Woofer is a great choice for small volume closed boxes. It has a standard design, in a closed box, of 8.2L with a F3 at 73hz and a "Q" at 0.7.
I have a made a simulation with a cheap Dayton Audio ND105-PR passive radiator, and it yields the F3 a 61hz, which is more or less what I'm looking for.
I have read somewhere that a "rule of thumb" is to use a passive radiator twice as big as the woofer (or two at the same size). This is unfortunately not possible in my design, and doesn't seem to change the F3 in the simulations either.
In most designs the PR is places on the side of the box, but would it be okay to place it just above the woofer as shown here:
I must admit that it is quite challenging and takes a lot of research to build a speaker in the sub 15L area, with both good loudness and a "deep" bass
.If any of you have some good recommendations for the woofer or PR it would be a great help
-Niels
Hi Niels,
Never cared for passive radiators. What does the Moral woofer look like in a sealed box? Run the numbers and show the graph please.
Place the tweeter close to the woofer if you can. Remember that you have to subtract the volume taken by the speakers and bracing, plus a passive radiator or a port. This is in general, not specific to your design. The light pack with fiberglass will help bring some of that back if you forget, but if you box is small for that woofer, you definitely want to use the fiberglass. The volume taken up by bracing and other things can surprise you. Don't fail to figure this out!
-Chris
Never cared for passive radiators. What does the Moral woofer look like in a sealed box? Run the numbers and show the graph please.
Place the tweeter close to the woofer if you can. Remember that you have to subtract the volume taken by the speakers and bracing, plus a passive radiator or a port. This is in general, not specific to your design. The light pack with fiberglass will help bring some of that back if you forget, but if you box is small for that woofer, you definitely want to use the fiberglass. The volume taken up by bracing and other things can surprise you. Don't fail to figure this out!
-Chris
"PR" is "same" as a vent with this difference:
If a speaker cone approaches the speed of sound, distortion is huge. However we normally can not drive a speaker this fast.
Around vent resonance, air displacement in the port is similar to air off the cone. If cone and vent areas are similar, velocity is similar. But we often see 4" vents with 12" cones. Vent area hardly over 1/10th cone area. So vent velocity is about 10X cone velocity. We often have "chuffing" or other extraneous noises at high bass output. Chamfering the port ends helps slightly. We may run a larger port if it is also longer. But pretty soon the total volume used by the port is a significant deduction from box volume.
Replace the port with a weighted diaphragm. The weight (mass) acts like a longer duct, but without using much volume.
I have never seen 2X PR; usually the PR is same as the main cone but with dummy weight and no magnet. I suppose extremer designs would double-up.
If a speaker cone approaches the speed of sound, distortion is huge. However we normally can not drive a speaker this fast.
Around vent resonance, air displacement in the port is similar to air off the cone. If cone and vent areas are similar, velocity is similar. But we often see 4" vents with 12" cones. Vent area hardly over 1/10th cone area. So vent velocity is about 10X cone velocity. We often have "chuffing" or other extraneous noises at high bass output. Chamfering the port ends helps slightly. We may run a larger port if it is also longer. But pretty soon the total volume used by the port is a significant deduction from box volume.
Replace the port with a weighted diaphragm. The weight (mass) acts like a longer duct, but without using much volume.
I have never seen 2X PR; usually the PR is same as the main cone but with dummy weight and no magnet. I suppose extremer designs would double-up.
Hi, yes. Often the PR is the same size as the woofer, or one size up from it. My experiences with PRs is that they are hard to control. Once set in motion, they tend to decay on their own time it seems. Because the mass of the air in the port is so low, it's very easy to control what the port is doing. They just don't seem to be as dynamic as a real ported system can be.
-Chris
-Chris
Quite different, as it doesn't cut off as dramatically. Maybe I could even boost the f3 to 60hz with the DSP - what do you think?
Also, this pink fiberglass doesn't seem to have that name in Europe. Does anyone know what to search for?
Passive radiators seems to be used by a lot of bluetooth speakers out there, ranging from B&O to Harmann Kardon. What is the main reason for them using it, if it in most terms are better to just use a sealed box?
Hi Niels,
Now that looks like a response that would be useful. Because the LF cutoff frequency is so high you really are much better off using a sealed box that will always load the woofer. I happen to like large, ported enclosures. Small ported enclosures work well only if you make certain you don't drive them below their cutoff frequency.
You can supply a mild boost, but that comes at the expense of lower overall loudness before clipping. Do consider using this as an actively crossed over biamp system. If you did that, you could control the low frequency cut-off (by rolling it off) which would buy you more useable power because there wouldn't be a passive crossover and you can save all the power that would have been wasted in the low bass department. It would be a much cleaner system that would play at higher levels.
-Chris
Now that looks like a response that would be useful. Because the LF cutoff frequency is so high you really are much better off using a sealed box that will always load the woofer. I happen to like large, ported enclosures. Small ported enclosures work well only if you make certain you don't drive them below their cutoff frequency.
You can supply a mild boost, but that comes at the expense of lower overall loudness before clipping. Do consider using this as an actively crossed over biamp system. If you did that, you could control the low frequency cut-off (by rolling it off) which would buy you more useable power because there wouldn't be a passive crossover and you can save all the power that would have been wasted in the low bass department. It would be a much cleaner system that would play at higher levels.
-Chris
Now you have. F&R of a bi-amped 4 way
In the old days this was true. Not anymore so much. Some even experiment with leaving the motor intact and shorting the leads when converting an old woofer.
Yes.
We learned long ago it really is better to double or one size up at minimum.
I have had different experiences than you. I very much enjoy a good PR system.
Drone cones are what they are. Often they can be better implemented than other systems when there is need to keep it compact.
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